Researchers built an experimental thin-film solar cell prototype by coating materials with carbon from solution, which may have a big future impact, especially in applications for flexible solar cells, such as on windows or buildings.

"Carbon has the potential to deliver high performance at a low cost. To the best of our knowledge, this is the first demonstration of a working solar cell that has all of the components made of carbon." - Zhenan Bao, professor and senior author of the study

The process that the team developed for coating the solar cells is also a big step forward in solar cell technology, as they were able to build their device without expensive machines or tools, which is vastly different from the techniques currently used for manufacturing silicon solar cells.

The researchers replaced the silver and indium tin oxide (ITO) used in conventional solar cell electrodes with graphene (one-atom-thick sheets of carbon) and single-walled carbon nanotubes, and the photoactive layer was made with carbon nanotubes and buckyballs (carbon molecules with a one nanometer diameter).

Right now, the all-carbon cell has an efficiency of less than 1% due to the fact that it primarily absorbs near-infrared wavelengths, but researchers are investigating ways to improve that efficiency, including experimenting with other nanomaterials that can absorb a wider range of wavelengths.

There have been other claims of all-carbon solar cells, but according to researchers, theirs is the first to be truly "all carbon":

"Every component in our solar cell, from top to bottom, is made of carbon materials. Other groups have reported making all-carbon solar cells, but they were referring to just the active layer in the middle, not the electrodes." - Michael Vosgueritchian, co-lead author of the study